#include <iostream>
#include <algorithm>
#include <cstdio>
#include <array>
using namespace std;
#ifdef ONLINE_JUDGE

//#define getchar() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1 << 21, stdin), p1 == p2) ? EOF : *p1++)
//char buf[1 << 23], *p1 = buf, *p2 = buf, ubuf[1 << 23], *u = ubuf;

#endif
int read() {
	int p = 0, flg = 1;
	char c = getchar();
	while (c < '0' || c > '9') {
		if (c == '-') flg = -1;
		c = getchar();
	}
	while (c >= '0' && c <= '9') {
		p = p * 10 + c - '0';
		c = getchar();
	}
	return p * flg;
}
void write(int x) {
	if (x < 0) {
		x = -x;
		putchar('-');
	}
	if (x > 9) {
		write(x / 10);
	}
	putchar(x % 10 + '0');
}
bool _stmer;

const int N = 3e6 + 5;

char strbuf[N];

bool _edmer;
int main() {
	cerr << (&_stmer - &_edmer) / 1024.0 / 1024.0 << "MB\n";
#ifndef cxqghzj
	freopen("song.in", "r", stdin);
	freopen("song.out", "w", stdout);
#endif
	scanf("%s", strbuf);
	string s = strbuf;
	int ans = 1;
	for (int i = 0; i < s.size() - 1; i++)
		if (s[i] == 'B' && s[i + 1] == 'A') ans++;
	write(ans), puts("");

	return 0;
}
